The adaptive significance of monoecism in Cnidoscolus urens (L.) Arthur (Euphorbiaceae)

Cnidoscolus urens is a monoecious, selfcompatible herb. Male and female flowers differ structurally, but appear superficially similar and the principal dry season pollinator, a butterfly (Eurema daira) did not discriminate between them. Female flowers offered little or no nectar reward and may mimic males in order to receive pollen. Male flowers last only 1 day; female flowers usually last 1 day but may remain receptive for 7 days if unpollinated. Flowers opened between 00.00 hours and 01.00 hours, opening earlier as the wet season approached. This shift is probably correlated with a change to nocturnal moth pollination in the wet season.
Within an inflorescence there are c. 16 times more male than female flowers. Female flowers occur in the lowermost positions and open first. Female flowering is followed by a brief period when no flowers open and then by an extended period of male flowering.
Although there is no overlap between male and female phases within an inflorescence, nonsynchronous development of several inflorescences on one individual means that selfing is possible for nearly all female flowers. However, observations of pollinator behaviour indicate that butterflies frequently move to another plant after visiting one inflorescence. Thus there is a large degree of outcrossing in practice.     

Significance of intra-inflorescence variation on flowering time of a spring ephemeral, <Emphasis Type="Italic">Gagea lutea</Emphasis> (Liliaceae), under seasonal fluctuations of pollinator and light availabilities

I studied the relationship between seed-set patterns within inflorescences and temporal variations in light and pollinator availabilities for 2 years in the spring ephemeral species Gagea lutea in a deciduous forest. Timing of canopy closure and seasonal trend of pollinator frequency did not synchronize with the annual fluctuation in flowering phenology. In the early snowmelt year, seed-set success reflected the seasonal pollinator abundance from early to middle flowering periods. In the late snowmelt year, however, seed-set rates were independent of pollinator activity and decreased with canopy closing even after hand pollination. The restricted seed production by defoliation and the increase in seed-set rates at the forest edge suggested that seed production was supported by current photosynthetic carbon gain. Thus, annual fluctuations of reproductive success can explain the variation in flowering phenology within a population although seasonal light deterioration would serve as a selective force for flowering in the early season.     

北京地区蒿柳的开花物候期及单花序开放过程中花粉活力和柱头可授性变化

Flowering phenology and flowering dynamics of female and male inflorescences of Salix viminalis Linn. in Beijing were observed in 2015 and 2016, and changes in pollen activity and stigma receptivity were also investigated. The results show that early flowering stage of S. viminalis in Beijing is happened in early?March, flowering period is 11-18 d, and flowering pattern is the first opening type of male flower. Flowering period of single inflorescence in male and female plants is 10-15 d and 8-10 d, respectively, which can be divided into five stages:emerging color stage, initial flowering stage, half flowering stage, full flowering stage and withered stage. Flowering date of male plant is earlier about 3-4 d than that of female plant. However, the difference of full flowering stage between male and female plants is only 1 d. Pollen germination rate and stigma receptivity show a trend of firstly increasing then decreasing during blossom process. Pollen germination rate reaches the highest of 72% at full flowering stage, and stigma receptivity is more than 90% at half and full flowering stages. Therefore, it is suggested that pollen collection and pollination in mid?March can improve success rate of cross breeding of S. viminalis.     

心叶凹唇姜的开花格局和雄性先熟机制

心叶凹唇姜 (Boesenbergia longiflora) 是分布于亚洲热带的一种姜科植物, 在我国滇南地区成片生长于石灰山贫瘠的岩石缝隙和路边林下的冲积土壤上。心叶凹唇姜的花寿命为两天, 第1天为严格的雄性阶段, 第2天为严格的雌性阶段, 是典型的花内雄性先熟, 一朵花的雌、雄性阶段没有重叠, 因而完全避免了自花授粉的发生。对这两种生境 (石灰山贫瘠的岩石缝隙和路边林下) 下的心叶凹唇姜的4个野外种群 (在云南省普洱市的翠云乡彩虹洞、南岛河、澜沧县惠民乡和西双版纳州绿石林森林公园) 和栽培植株的开花格局进行调查后发现, 大多数个体在同一时间内只有一个花序开花, 并且每隔一天才开一朵花, 只有10%左右的植株同时具有雄性阶段和雌性阶段的花, 这样的开花格局有效地降低了同株异花授粉发生的可能。心叶凹唇姜的平均花粉-胚珠比 (Pollen-ovuleratio) 为291, 应该是以异交为主的混合交配系统。其自然种群存在着花粉限制, 彩虹洞、南岛河和绿石林3个不同种群的平均结籽率都不到60%, 这可能与其较小的花展示有关。心叶凹唇姜为泛化传粉植物, 不同种群的有效传粉昆虫种类各不相同。在两种不同的生境条件下, 心叶凹唇姜花的大小和开花格局都没有显著的差异, 大多数个体同时只具有一种性阶段的花, 说明心叶凹唇姜这种独特的开花格局是长期进化的结果。心叶凹唇姜通过隔一天开一朵花的开花格局, 配合雄性先熟机制, 有效地降低了自交的发生。     

3种雌雄异熟樟科植物开花动态的比较研究

为了解樟科植物雌雄异熟的繁育系统特点,对3种樟科植物阴香(Cinnamomum burmannii)、紫楠(Phoebe sheareri)和浙江楠(Phoebe chekiangensis)雌雄异熟花的开花动态进行了比较研究。结果表明,3种植物雌性功能期的开始时间、雌性功能期和雄性功能期的时间分配有差异。3种植物的主要传粉者均为中华蜜蜂,在雌性功能期和雄性功能期均有访花;在雌性功能期第四轮退化雄蕊蜜腺和雄性功能期第三轮花丝基部的蜜腺分泌花蜜,不同开花阶段的花蜜蜜量和含糖量没有显著差异;柱头可授性和花粉活力在雌性和雄性功能期均较高;雌性功能期和雄性功能期均有自然花粉落置;座果率均是异交补粉自然套袋,表明都存在一定的传粉限制。因此,樟科植物雌、雄性阶段时间分配的不同,可能与退化雄蕊蜜腺和第三轮雄蕊附属蜜腺的分泌节律有关。     

深山含笑传粉生物学研究

为明确深山含笑(Michelia maudiae)的传粉生物学特性,该文以西华师范大学校园内的深山含笑为研究材料,采取野外观察法记录了深山含笑的开花动态、访花者及访花频率;用游标卡尺法,测定了深山含笑的异交指数(OCI);用醋酸洋红法,测定了花粉胚珠比(P/O);用套袋和人工授粉法,测定了深山含笑的繁育系统。结果表明:(1)深山含笑为早春开花植物,其种群花期为2~3月,持续30d左右,单花花期5~6d;在单花开放初期,最内层的花瓣未绽开,是适应潮湿或多雨的环境而保护花药与柱头免受雨水的冲刷,提高雌雄性适合度,确保繁殖成功的一种策略;(2)深山含笑的有效传粉者为蜜蜂,访花时间集中在晴朗天气的中午;(3)深山含笑的异交指数(OCI)等于5,花粉胚珠比(P/O)为2 933±50;(4)深山含笑为雄蕊先熟,柱头可授性在开花第2~3天达到最高;(5)套袋和人工授粉表明深山含笑为兼性自交和异交授粉,其中异交授粉的座果率和结籽率显著高于自交授粉。早春开花的深山含笑,其传粉者为单一的蜜蜂,繁育系统为异交,部分自交亲和,结果为引种栽培、良种选育等提供依据更好地利用和保护此资源奠定基础。     

Increased maleness at flowering stage and femaleness at fruiting stage with size in an andromonoecious perennial, Veratrum nigrum

Theory predicts that cosexual plants should adjust their resource investment in male and female functions according to their size if female and male fitness are differentially affected by size.However,few empirical studies have been carried out at both the flowering and fruiting stages to adequately address size-dependent sex allocation in cosexual plants.In this paper,we investigated resource investment between female and male reproduction,and their size-dependence in a perennial andromonoecious herb,Veratrum nigrum L.We sampled 192 flowering plants,estimated their standardized phenotypic gender,and assessed the resource investment in male and female functions in terms of absolute dry biomass.At the flowering stage,male investment increased with plant size more rapidly than female investment,and the standardized phenotypic femaleness (ranging from 0.267 to 0.776) was negatively correlated with plant size.By contrast,female biased allocation was found at the fruiting stage,although both flower biomass and fruit biomass were positively correlated with plant size.We propose that increased maleness with plant size at the flowering stage may represent an adaptive strategy for andromonoecious plants,because male flowers promote both male and female fertility by increasing pollinator attraction without aggravating pollen discounting.     

Pollinator response to female and male floral display in a monoecious species and its implications for the evolution of floral dimorphism

Pollinator-mediated selection has been hypothesized as one cause of size dimorphism between female and male flowers. Flower number, ignored in studies of floral dimorphism, may interact with flower size to affect pollinator selectivity. In the present study, we explored pollinator response, and estimated pollen receipt and removal, in experimental populations of monoecious Sagittaria trifolia, in which plants were manipulated to display three, six, nine or 12 female or male flowers per plant. In this species, female flowers are smaller but have a more compressed flowering period than males, creating larger female floral displays. Overall, pollinators preferred to visit male rather than female displays of the same size. Both first visit per foraging bout and visitation rates to female displays increased with display size. However, large male displays did not show increased attractiveness to pollinators. A predicted relationship that pollen removal, rather than pollen receipt, is limited by pollinator visitation was confirmed in the experimental populations. The results suggest that the lack of selection on large male displays may affect the evolution of floral dimorphism in this species.     

Seasonal changes in pollinator activity influence pollen dispersal and seed production of the alpine shrub Rhododendron aureum (Ericaceae)

In alpine ecosystems, microscale variation in snowmelt timing often causes different flowering phenology of the same plant species and seasonal changes in pollinator activity. We compared the variations in insect visitation, pollen dispersal, mating patterns, and sexual reproduction of Rhododendron aureum early and late in the flowering season using five microsatellites. Insects visiting the flowers were rare early in the flowering season (mid-June), when major pollinators were bumblebee queens and flies. In contrast, frequent visitations by bumblebee workers were observed late in the season (late July). Two-generation analysis of pollen pool structure demonstrated that quality of pollen-mediated gene flow was more diverse late in the season in parallel with the high pollinator activity. The effective number of pollen donors per fruit (N(ep)) increased late in the season (N(ep) = 2.2-2.7 early, 3.4-4.4 late). However, both the outcrossing rate (t(m)) and seed-set ratio per fruit were smaller late in the season (t(m) = 0.89 and 0.71, seed-set ratio = 0.52 and 0.18, early and late in the season, respectively). In addition, biparental inbreeding occurred only late in the season. We conclude that R. aureum shows contrasting patterns of pollen movement and seed production between early and late season: in early season, seed production can be high but genetically less diverse and, during late season, be reduced, possibly due to higher inbreeding and inbreeding depression, but have greater genetic diversity. Thus, more pollinator activity does not always mean more pollen movement.     

观赏海棠杂交后代萌芽期观察及花期预测的灰色关联度分析

以‘国光’苹果（Malus domestica‘Rails’）为母本,以10个观赏海棠品种（Malus spp．）为父本进行杂交育种,对杂交后代实生群体的萌芽期进行了观察,并根据9株2年即开花单株的童期性状对观赏海棠的花期进行了灰色关联度分析。结果显示,所有观赏海棠杂交后代的萌芽期（3月12日以后）均晚于父本,93．89％的杂交后代萌芽期（3月下旬至4月上旬）与母本相近或稍晚于母本。在观赏海棠杂交后代花期的叶片叶绿素含量、可溶性蛋白质含量、叶面积、株高、地径等指标以及童期的萌芽期和展叶期等7个性状中,萌芽期和展叶期与花期的灰色关联度最大。因此,在童期利用叶片萌芽期对观赏海棠的花期进行预测极具可行性。     

早春短命植物黑鳞顶冰花的花粉呈现时序及其适应性

花粉的时序呈现是指植物花药按一定次序释放花粉的现象, 被认为是对传粉者访问频率的一种适应。在传粉者充足的环境中, 植物通过限制花粉1次被移出的数量, 使花粉供体能作为多个父本, 从而提高雄性适合度。该文从开花习性、花部特征、传粉者及繁育系统等方面对早春短命植物黑鳞顶冰花(Gagea nigra)的花粉呈现时序及其适应性进行研究, 结果表明, 黑鳞顶冰花单花期约5-7天; 白天开放, 晚上闭合, 花药次序开裂, 呈拉链式散粉, 散粉期4-6天。黑鳞顶冰花以异交为主, 部分自交亲和。蝇类和食蚜蝇为主要传粉者, 访花频率为(0.141±0.078) flower∙h^-1。在雄蕊的时序散粉过程中, 雌蕊持续生长, 经历了从低于雄蕊到等高、再到高于雄蕊阶段。在等高阶段, 单花早晚的开闭, 使得雌雄蕊紧靠在一起, 促成了自动自花授粉。在传粉者缺乏的环境中, 黑鳞顶冰花的花粉时序呈现延长了散粉期, 在等待传粉者和分摊风险方面具重要作用。这种花粉渐次呈现的策略, 在新疆的早春开花植物中可能广泛存在。     

Pollination ecology of Gentiana siphonantha (Gentianaceae) and a further comparison with its sympatric congener species

In this study, we studied pollination ecology of Gentiana siphonantha (Gentianaceae), a late-autumn flowering alpine perennial in the northeastern Qinghai-Tibetan Plateau for two years for the first time. We also aimed to compare the pollination differentiation between this species and sympatrically distributed G. straminea that has a close phylogenetic origin but is flowering early. Flowers of G. siphonantha are characteristic of di-chogamy and herkogamy and this floral development prevents occurrence of autonomous self-pollination. This implication was confirmed by the breeding experiments, since no seed was produced when flowers were isolated. However, this gentian proved to be highly self-compatible when geitonogamous selfing was artificially induced. Each individual plant of this species has an average of 14.6 flowers ranging from 4 to 31, at both staminate and pistillate stages with a ratio of 1.2:1 in full anthesis. Both floral development and breeding experiments suggested that pollen vectors were indispensable for successful seed sets of this species. A great variety of insects were observed to visit this species, but the most common and only legitimate pollinator is Bumbus sushikini. A statistic observation suggested that this pollinator showed no preference to either staminate or pistillate flowers and visited them at random. We further calculated the frequency of their visits between and within individual plants. Among the pollinators’ bouts, the proportions of geitonogamous visits within an individual plant occupy about 87.8%. Such a case implied that geitonogamous selfing prevails in this species in spite of floral dichogamy and her-kogamy that were suggested to promote outcrossing. Compared with sympatric G. straminea, the total floral longevity and the male and female duration of this species are shorter. However, the number of flowers of each individual plant and branch increased when in full anthesis. It is interesting that both closely related species shared the same pollinator despite their distinct difference in flower morphology. This finding is inconsistent with the previous hypothesis that both flower color and corolla tube depth have coevolved with different pollinators during speciation and formation of reproductive isolation. Both visit frequencies of the individual flower and geitonoga-mous visits within the individual plant are higher in G. siphonantha than in G. straminea. This difference may result from their different inflorescence designs that actively act upon behaviors of pollinator. Although these two species differed in flowering phenology, their flowering stages overlapped for a few days, suggesting incomplete pollination isolation between them.     

Impact of plant flowering phenology on the cost/benefit balance in a nursery pollination mutualism,with honest males and cheating females

This study documents the flowering phenology and its potential consequences on a nursery pollination mutualism between a dioecious plant, in which honest male plants, but not cheating females, allow the specific pollinator to reproduce within inflorescences. Very few pollinators were found to emerge during plant anthesis, leading to a low (if any) potential benefit through pollen dispersal. This opens the question why male plants do not also cheat their pollinators. Female plants flowered late in the season, when many males had just achieved their own anthesis, which increased the efficiency of pollen transfer. Finally, some late‐flowering males reached their anthesis simultaneously with females, which open the possibility for pollinator to choose between honest males and cheating females. Nevertheless, female plants were found to produce fruits, even though fruit production was limited by pollen (and pollinator) supply, meaning that cheating was not entirely retaliated by the mutualistic partner.     

Pollinators and Reproductive Success of the Wild Cucurbit Cucurbita maxima ssp. andreana (Cucurbitaceae)

Abstract: We studied the reproductive success and pollinators of Cucurbita maxima ssp. andreana in different disturbed habitats where it grows naturally. Data were obtained from three populations. One grew within a soybean crop, the other within a corn crop, and the third in an abandoned crop field. Cucurbita maxima ssp. andreana is an annual vine with a flowering period from December to April. Male flowers appear first, thereafter female and male flowers appear together. Flower lifetime (9 h) was similar in male and female flowers. The pollinator guild was comparable for the three populations but some differences in the frequency of the insect species were observed. Native bees were the main pollinators in the population in the abandoned field, while beetles pollinated the populations in crop fields. These differences were not linked with the pre-emergent reproductive success, fruit and seed set, or fruit quality. This is a self-compatible plant. Fruit and seed set and fruit traits (total mass, width and length of fruits, number of seeds per fruit, and seed mass) did not show significant differences between hand-cross and hand-self pollinated flowers. This wild cucurbit is a generalist with respect to pollinator guild, and flower visitors seem to be highly efficient in pollen transference. Cucurbita maxima ssp. andreana is well adapted to disturbed habitats because plants ripened fruits successfully, regardless of the group of insects visiting flowers.     

Impact of volcanic activity on a plant-pollinator module in an island ecosystem: the example of the association of <Emphasis Type="Italic">Camellia japonica</Emphasis> and <Emphasis Type="Italic">Zosterops japonica</Emphasis>

Volcanic activity provides an indispensable opportunity to study the ecological responses of organisms to environmental devastation. We examined the reproductive success of Camellia trees to identify how volcanic activity affects the processes of leaf survival, flowering activity, fruit and seed production, pollinator abundance, pollinator visitation frequency, pollination rate, and fruit and seed maturation at different damage sites on Miyake-jima, which experienced an eruption in the summer of 2000. Volcanic gases negatively affect leaf survival and reduce flowering activity in heavily damaged areas. Pollen transfer was sufficient to ensure that higher pollination rates (83%) occurred in heavily damaged areas than in less damaged areas (26–45%), but pollinator densities were lower in response to reduced flower resources. Fruit abortion rates were greater in heavily damaged sites (78%) than in less-damaged sites (53–63%). Consequently, fruit-set rates (16–29%) did not differ significantly among sites. Seed set rates tended to increase with increasing volcanic damage. The negative correlation between seed-set rates and seed mass suggests that the decreased seed mass in severely damaged sites was attributable to the better pollination rates observed there. These results indicate that compensation mechanisms ensure better reproductive success at sites that are more strongly affected by volcanic activity.     

Relative importance of diurnal and nocturnal pollinators for reproduction in the early spring flowering shrub Stachyurus praecox (Stachyuraceae)

Generalized pollination systems may be favored in early spring flowering plants, as during this period pollinator activity is unpredictable. Many previous studies have concentrated on the importance of diurnal visitors in pollination, and consequently, information on the contribution of nocturnal visitors to pollination in early spring is limited. This study was conducted to evaluate the relative importance of diurnal and nocturnal pollinators in the early spring flowering dioecious shrub Stachyurus praecox (Stachyuraceae), in two temperate forests in central Japan. Visitors to the female and male flowers were observed during day and night, and their relative contributions to seed set were compared. The pollinator observations revealed that the diurnal and nocturnal insects visited both male and female flowers, and that the main flower visitors were diurnal small bees and flies as well as nocturnal settling moths. The diurnal and nocturnal flower visitors also acted as pollinators, as the pollen grains of S. praecox were attached to the insects collected from the female flowers. Pollination experiments demonstrated that the contributions of diurnal pollinators to the seed set were higher than those of the nocturnal pollinators. The results of this study indicate that S. praecox has a generalized pollination system, comprising both diurnal insects and nocturnal settling moths. Although the roles of diurnal insects are more important in the pollination of S. praecox, nocturnal settling moths may have a complementary role in early spring.     

宁夏枸杞的花粉呈现式样及交配系统研究北大核心CSCD

被子植物的花回馈、雌雄蕊时空分离特征和花粉呈现式样等花部特征及传粉者效率会影响雄性适合度和有性繁殖过程。宁夏枸杞(Lycium barbarum)是中国宁夏、新疆、内蒙等干旱和半干旱地区分布的特有种。该研究对新疆喀什地区宁夏枸杞自然种群的花部综合征、花粉呈现式样、花回馈、传粉者行为与交配方式的关系进行观察及统计分析,以探讨其花粉逐步呈现的适应性及其在提高雌雄繁殖过程中的意义。结果表明:(1)宁夏枸杞的单花寿命为(4.07±0.15) d,而雄性持续时间(0.07±0.01 d)比雌性持续时间短(4±0.01 d);花寿命内雌蕊长度比雄蕊长,属柱头探出式异位类型;花粉呈现式样为不完全逐步呈现。(2)花寿命不同阶段花回馈间存在显著差异。(3)意大利蜜蜂(Apis mellifera)、熊蜂(Bombus sp.)、食蚜蝇(Syrphidae sp.)是宁夏枸杞在自然居群的主要访花者,其中熊蜂和食蚜蝇是主要传粉者,但传粉者效率低,属于高移出低沉积类型。(4)宁夏枸杞的花粉胚珠比(2 448.11±448.32)及授粉实验结果均表现出兼性异交特征;自发自交及人工自花授粉花的座果率及结籽率很低,属于自交不亲和类型;自然传粉花的座果率及结籽率比人工去雄异花低,存在其较高的花粉限制(40.71%)。研究发现,宁夏枸杞花部综合征表现出雌雄异位和花粉不完全逐步呈现式样,这是避免雌雄功能及雄蕊各花药间的干扰、减少花粉同步移出及保障其雄性适合度的有效途径,但自然居群的传粉者种类限制、传粉效率低以及自交不亲性是导致宁夏枸杞花粉限制及降低雌性繁殖成功的主要原因。     

秦岭岩白菜的传粉生物学特性与繁育系统

对珍稀濒危植物秦岭岩白菜(Bergenia scopulosa T.P.Wang)的开花特性、传粉适应及繁育系统进行了分析研究。结果表明:(1)秦岭岩白菜为蝎尾状聚伞花序,具(29±10)朵单花,单花期约15d,遇低温雨雪天气花冠闭合,可延长3~5d,花序花期约30d,种群花期近4个月。(2)花粉活力在花药开裂后的12h内最高(约90%),维持单花平均花粉活力在30%以上约6d;柱头在第1~4天内保持很强的可授性,维持可授性的时间约为9d。(3)秦岭岩白菜主要有效传粉昆虫为中华蜜蜂,平均访花频率为6.5朵/min,单花停留时间为(11.0±4.8)s。(4)秦岭岩白菜的花粉胚珠比(P/O)为589.8,杂交指数(OCI)为3;人工授粉实验显示,秦岭岩白菜不存在无融合生殖,自交亲和,主动自交罕见,生殖成功主要依赖传粉者。研究认为,秦岭岩白菜是兼性异交的繁育系统,胚珠受精过程中可能存在自交衰退。     

Co-flowering plants support diverse pollinator populations and facilitate pollinator visitation to sweet cherry crops

Many food crops depend on animal pollination to set fruit. In light of pollinator declines there is growing recognition of the need for agro-ecosystems that can sustain wild pollinator populations, ensuring fruit production and pollinator conservation into the future. One method of supporting resident wild pollinator populations within agricultural landscapes is to encourage and maintain floral diversity. However, pollinator visitation to crop plants can be affected either positively (facilitation) or negatively (competition) by the presence of co-flowering plants. The strength and direction of the facilitative/competitive relationship is driven by multiple factors, including floral abundance and the degree of overlap in pollinator visitation networks. We sought to determine how plant-pollinator networks, within and surrounding sweet cherry (Prunus avium) orchards, change across key time points during the cherry flowering season, in three growing regions in Australia. We found significant overlap in the suite of flower visitors, with seven taxa (including native bees, flies, hoverflies and introduced honey bees, Apis mellifera) observed visiting cherry and other co-flowering species within the orchard and/or the wider surrounding matrix. We found evidence of pollinator facilitation with significantly more total cherry flower visits with increasing percent cover of co-flowering plants within the wider landscape matrix and increased visitation to cherry by honey bees with increasing co-flowering plant richness within the orchard. During the cherry flowering period there was a significant positive relationship between pollinator richness on cherry and pollinator richness on co-flowering plants within the orchard and the area of native vegetation surrounding orchards. Outside of the crop flowering season, co-flowering plants within the orchard and wider landscape matrix supported the same pollinator taxa that were recorded visiting cherry when the crop was flowering. This shows wild plants help support the pollinators important to crop pollination, outside of the crop flowering season, highlighting the role of co-flowering plants within pollinator-dependent cropping systems.     

胡杨、灰叶胡杨开花生物学特性研究

从居群水平研究了胡杨、灰叶胡杨不同居群的开花物候特征.结果表明:胡杨、灰叶胡杨各居群均表现为雄株开花物候早于雌株,一般可授期开始较散粉期晚1～4 d,结束较散粉期晚2～5 d,并且居群散粉期和可授期的重叠期较长.在同一居群内,胡杨、灰叶胡杨同性单株间开花期的不一致性较高.两个种相比较,胡杨居群的开花进程比灰叶胡杨居群早2～5 d,并且从每日开花株数累积分布来看,胡杨散粉期、可授期为双峰型,灰叶胡杨为单峰型.